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对比研究了不同含钙物质对碱激发胶凝材料凝结时间及强度的影响,并探讨了其影响机制。结果表明:除碳酸钙外,含钙物质具有强烈的促凝作用,由强到弱依次为氯化钙、氢氧化钙、氧化钙;适当掺量的上述含钙物质均具有增强作用,但过量的含钙物质因试样快凝导致强度反而下降。上述含钙物质具有不同促凝增强机制。易溶的氯化钙具有提供非均匀成核基体及生成低钙硅比水化硅酸钙凝胶的共同作用机制,导致少量氯化钙(1.0%)就可使试样凝结时间缩短至10 min以内,但其增强作用只体现于早期。微溶的氢氧化钙只存在"生成凝胶"这单一作用机制,其促凝增强效果变弱。氧化钙与溶液作用生成氢氧化钙,作为非均匀成核基体而促进硅铝聚合反应,但其与溶液作用历时较长,掺量高达5%时才使试样快凝。难溶的碳酸钙溶解度极低,不具备形成非均匀成核基体和生成凝胶的促凝增强机制。
Abstract：The setting time and strength of alkali-activated cementitious materials(AAM) with different calcium species were investigated. The results show calcium species except calcium carbonate have a significant acceleration effect on setting and hardening. Calcium chloride is the most dominant accelerator among calcium species(i.e., calcium chloride, calcium hydroxide, calcium oxide and calcium carbonate). Besides calcium carbonate, the other three calcium species enhance the strength, but the excessiveness cause a decrease in the strength due to the rapid hardening. The different calcium sources exhibit different mechanisums of shortening the setting time and enhacing the strength. Calcium chloride, as a readily soluble salt, provides the precipitaion of heterogeneous uncleation centers and the formation of calcium silicate hydration gels with a low Ca/Si ratio.The combined effects above lead to a shorter setting time of pastes with 1.0% calcium chloride(i.e., <10 min). However, the improved effect of calcium chloride on strength is only valid at early stage. Calcium hydroxide, as a sparingly soluble compound, also causes the formation of gels that shortens the setting time and enhances the strength, but its effectiveness becomes poor because there is no coupling effect of nucleation centers. Calcium oxide can react in solution to form calcium hydroxide that provides the nucleation templates to accelerate geopolymerization, but the duration of this reaction is longer, so that the rapid hardening just occurs in pastes with a high volume of 5%. Calcium carbonate, as an insoluble salt, does not provide any acceleration effect.
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基本信息:
DOI：10.14062/j.issn.0454-5648.2017.08.08
中图分类号:TQ177
引用信息:
[1]叶家元,张文生,史迪.钙对碱激发胶凝材料的促凝增强作用[J].硅酸盐学报,2017,45(08):1101-1112.DOI:10.14062/j.issn.0454-5648.2017.08.08.
基金信息:
国家自然科学基金项目(51572252);; 国家“863”计划课题(2015AA034701)资助
2016-09-14
2016
2017-06-25
2017-06-01
2017
1
2017-07-23
2017-07-23
2017-07-23